Evaluation of the effects of suspension formulation on the viability of probiotic Lactobacillus isolate in cryopreservation

BACKGROUND AND OBJECTIVESProbiotics are important starters in the food and pharmaceutical industries. Their long-term maintenance is an important factor. These bacteria can be stored for a long time using freezing techniques like freeze-drying. However, freeze-drying damages bacterial cells. Therefore, to protect the bacteria, it is necessary to use cryoprotectants to increase bacterial survival.MATERIALS AND METHODSIn this experiment, lactose, cellobiose, sucrose, trehalose, and maltose were used as cryoprotectants at concentrations of ۸%, ۱۶%, and ۲۴%. After culturing the bacteria, the desired cryoprotectant at different concentrations was added to the bacteria, followed by freeze-drying. Subsequently, the viability of the bacteria after freeze-drying was assessed.RESULTS AND DISCUSSIONThe protective role of disaccharides is to maintain the stability of the cell membrane during freezing by reducing the formation of intracellular ice. After comparing the effects of different concentrations of sugars on bacterial viability, there was no significant difference in the survival of bacteria at ۸% sugar concentration. At the concentration of ۱۶%, trehalose and sucrose showed the highest viability rates, while lactose and cellobiose showed the lowest viability rates. At the concentration of ۲۴%, trehalose had the highest survival rate, while cellobiose and lactose had the lowest survival rates.CONCLUSIONUsing lactose and cellobiose as cryoprotectants resulted in lower viability rates of bacteria compared to other sugars. Therefore, these two sugars are not suitable options as cryoprotectants. The highest survival rate was observed with trehalose and sucrose. Sucrose directly interacts with lipids and proteins, replacing the hydrogen bonds that normally exist in water. Trehalose, which has a high glass transition temperature (Tg), can significantly reduce the formation of ice crystals, thereby reducing mechanical damage to the cell membrane. The protective role of trehalose may be due to its stabilizing capacity for proteins, which replaces water around polar molecules.

کلیدواژه ها:

probiotics ، freeze-drying ، cryoprotectant ، disaccharide